By April 1972, the American military presence in Vietnam had largely been reduced to air power. North Vietnam launched their Easter Offensive — the largest military invasion since China crossed the Yalu River during the Korean War. Soon, the 5th Division of the Army of the Republic of Vietnam'(ARVN) was surrounded by three enemy divisions at An Loc, the capital of Binh Phuoc province. Their only hope of the defenders was American air power, calling on B-52s and AC-130 gunships to hammer the enemy infantry and armor. The ARVN troops were holding out, but badly needed supplies. The roads to...